A support for a cylindrical screen in a rotation screen printing apparatus, wherein the screen is received at both sides of the apparatus in a respective turnbuckle. The turnbuckle is supported for rotation in an intermediate ring.
Printing outlines for the rotation screen printing are produced out of so called SCREENY(copyright) screen printing plates that are mounted in the printing apparatus as cylinders. This material consists of a fine mesh stabilized steel fabric and is allowed to be loaded only by tension (axial loading of the cylindrical screen). As much as possible, uniform screen tension at standstill is to be sought, because during the printing process, the doctor blade located inside, exerts in additional and differing moment of torsion.
Locally, highly differing screen tensions cause the formation of waves at the circumference of the screen.
The inherent stability of the screen is ensured by the cylindrical shape.
When mounting, and during the printing process, the screen is variously loaded due to a plurality of reasons:
the design of turnbuckle with the conventional U-shaped recess causes at a axial loading and a tilting of the bearing.
The devices for the production of the screens have deviations, or may be soiled by residual adhesive agents, so that the outer stencil rings are not aligned precisely to each other.
At the axial tension, which is necessary for the screen, the side plates with the bearing are deformed so that the directions of the axes extend at an angle relative to each other.
General tolerances in printing apparatus can lead to various mistakes, e.g., to a deviation from the coaxial position of the positions of the bearings relative to each other.
Experience has shown that the pivotal movement at the sides of screens for a compensation of all causes shall amount maximally up to 0.5xc2x0. When no compensation can take place, the forming of waves at the printing screen is observed. These waves shorten the useful lifetime of the screen and lead to early failures of screens and to losses of the quality of the print.
Also, the screen cannot transmit any moments. Thus, an equalizing without a restoring moment must proceed practically without any force.
It is an object of the present invention to find a screen support that can equalize under an axial loading all influences for an unequal screen tension.
The proven turnbuckle with a U-shaped receptacle is used. The support is planar design and that lends itself to an integrating at both sides in the side plates.
A simple spherical support may indeed provide an equalization. Such a configuration, necessitates however, a large expenditure regarding the design for axial movements. The reliable functioning of a large embracement is needed, otherwise the ball acts like wedge. Should it be designed as a spherical sleeve bearing, the dimension of the design and speed of rotation are critical.
A purely universal joint bearing features similar drawbacks.
This solutions includes substantially a planar intermediated ring that is held resiliently in the side flange so that besides a pivoting relative to the side flange, a displacing in axial direction is also possible.